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Should Ecological Science Be Ethical?
Both scientific and moral communities have identified that current management of the natural environment by humans is unsustainable. How society responds to environmental challenges will likely require a multi-disciplinary approach. Jenkins addresses the contributions that science, religion and ethics can make to resolving complex environmental problems and increasing successful management of ecological systems. While we agree with many of Jenkins' points, he touches upon three common ideas about science, and ecology in particular, that we argue are often misconstrued: Scientific understanding of current environmental challenges is inadequate due to 'uncertainty' in scientific studies; Ecological scientists are equivalent to environmental managers; and scientists should become more like activists and consider social values as drivers. We suggest that these ideas may be unhelpful in interpreting scientific studies and might lead to increasing misrepresentation of science. Furthermore, such perceptions may increase distrust by the general public of scientists who do not adequately separate objective scientific evidence from personal value-judgments. We agree that the scientific method should indeed be ethical, with no room for fraud or deliberate falsification of results, but that the science itself must be objective and non-moral, with scientific evidence unprejudiced by political and social agendas. We recommend that ecologists and managers, as well as ethicists and religious communities, work together in a robust defense of an evidence-based approach to the management and restoration of global ecological systems
Density dependence across multiple life stages in a temperate old-growth forest of northeast China
Recent studies on species coexistence suggest that density dependence is an important mechanism regulating plant populations. However, there have been few studies of density dependence conducted for more than one life-history stage or that control for habitat heterogeneity, which may influence spatial patterns of survival and mask density dependence. We explored the prevalence of density dependence across multiple life stages, and the effects of controlling for habitat heterogeneity, in a temperate forest in northeast China. We used generalized linear mixed-effects models to test for density-dependent mortality of seedlings and spatial point pattern analysis to detect density dependence for sapling-to-juvenile transitions. Conspecific neighbors had a negative effect on survival of plants in both life stages. At the seedling stage, we found a negative effect of conspecific seedling neighbors on survival when analyzing all species combined. However, in species-level analyses, only 2 of 11 focal species were negatively impacted by conspecific neighbors, indicating wide variation among species in the strength of density dependence. Controlling for habitat heterogeneity did not alter our findings of density dependence at the seedling stage. For the sapling-to-juvenile transition stage, 11 of 15 focal species showed patterns of local scale (<10Â m) conspecific thinning, consistent with negative density dependence. The results varied depending on whether we controlled for habitat heterogeneity, indicating that a failure to account for habitat heterogeneity can obscure patterns of density dependence. We conclude that density dependence may promote tree species coexistence by acting across multiple life-history stages in this temperate forest. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-012-2481-y) contains supplementary material, which is available to authorized users
Regulation of STAT3 and its role in cardioprotection by conditioning: focus on non-genomic roles targeting mitochondrial function
Ischemiaâreperfusion injury (IRI) is one of the biggest challenges for cardiovascular researchers given the huge death toll caused by myocardial ischemic disease. Cardioprotective conditioning strategies, namely pre- and post-conditioning maneuvers, represent the most important strategies for stimulating pro-survival pathways essential to preserve cardiac health. Conditioning maneuvers have proved to be fundamental for the knowledge of the molecular basis of both IRI and cardioprotection. Among this evidence, the importance of signal transducer and activator of transcription 3 (STAT3) emerged. STAT3 is not only a transcription factor but also exhibits non-genomic pro-survival functions preserving mitochondrial function from IRI. Indeed, STAT3 is emerging as an influencer of mitochondrial function to explain the cardioprotection phenomena. Studying cardioprotection, STAT3 proved to be crucial as an element of the survivor activating factor enhancement (SAFE) pathway, which converges on mitochondria and influences their function by cross-talking with other cardioprotective pathways. Clearly there are still some functional properties of STAT3 to be discovered. Therefore, in this review, we highlight the evidence that places STAT3 as a promoter of the metabolic network. In particular, we focus on the possible interactions of STAT3 with processes aimed at maintaining mitochondrial functions, including the regulation of the electron transport chain, the production of reactive oxygen species, the homeostasis of Ca(2+) and the inhibition of opening of mitochondrial permeability transition pore. Then we consider the role of STAT3 and the parallels between STA3/STAT5 in cardioprotection by conditioning, giving emphasis to the human heart and confounders
SeedâtoâSeedling Transitions Exhibit DistanceâDependent Mortality but No Strong Spacing Effects in a Neotropical Forest
Patterns of seed dispersal and seed mortality influence the spatial structure of plant communities and the local coexistence of competing species. Most seeds are dispersed in proximity to the parent tree, where mortality is also expected to be the highest, because of competition with siblings or the attraction of natural enemies. Whereas distanceâdependent mortality in the seedâtoâseedling transition was often observed in tropical forests, few studies have attempted to estimate the shape of the survivalâdistance curves, which determines whether the peak of seedling establishment occurs away from the parent tree (JanzenâConnell pattern) or if the peak attenuates but remains at the parent location (Hubbell pattern). In this study, we inferred the probability density of seed dispersal and two stages of seedling establishment (new recruits, and seedlings 20 cm or taller) with distance for 24 tree species present in the 50âha Forest Dynamics Plot of Barro Colorado Island, Panama. Using data from seed traps, seedling survey quadrats, and treeâcensus records spanning the 1988â2014 period, we fit hierarchical Bayesian models including parameters for tree fecundity, the shape of the dispersal kernel, and overdispersion of seed or seedling counts. We combined predictions from multiple dispersal kernels to obtain more robust inferences. We find that Hubbell patterns are the most common and JanzenâConnell patterns are very rare among those species; that distanceâdependent mortality may be stronger in the seed stage, in the early recruit stage, or comparable in both; and that species with larger seeds experience less overall mortality and less distanceâdependent mortality. Finally, we describe how this modeling approach could be extended at a community scale to include less abundant species
Contrasting patterns of insect herbivory and predation pressure across a tropical rainfall gradient
One explanation for the extraordinarily high tree diversity of tropical lowland forests is that it is maintained by specialized natural enemies such as insect herbivores, which cause distance- and density-dependent mortality. Insect herbivory could also explain the positive correlation between tree species richness and rainfall if herbivory increases with rainfall, is higher on locally abundant versus rare species, and is not limited by predation pressure at wet sites. To test these predictions, insect herbivory and predation pressure on insect herbivores were quantified across a neotropical rainfall and tree species richness gradient, and herbivory was investigated in relation to local tree abundances. Insect herbivory on leaves (folivory) decreased strongly and significantly with rainfall, while predation pressure was significantly higher at the wetter site. Herbivores were more likely to attack abundant tree species, but herbivore damage levels were not related to tree species abundance. Insect folivores might contribute to local tree species coexistence in our system, but seem unlikely to drive the positive correlation between tree species richness and rainfall. The unexpected and contrasting patterns of herbivory and predation we observed support the need for a multi-trophic perspective to understand fully the processes contributing to diversity and ecosystem functioning
Local-Scale Drivers of Tree Survival in a Temperate Forest
Tree survival plays a central role in forest ecosystems. Although many factors such as tree size, abiotic and biotic neighborhoods have been proposed as being important in explaining patterns of tree survival, their contributions are still subject to debate. We used generalized linear mixed models to examine the relative importance of tree size, local abiotic conditions and the density and identity of neighbors on tree survival in an old-growth temperate forest in northeastern China at three levels (community, guild and species). Tree size and both abiotic and biotic neighborhood variables influenced tree survival under current forest conditions, but their relative importance varied dramatically within and among the community, guild and species levels. Of the variables tested, tree size was typically the most important predictor of tree survival, followed by biotic and then abiotic variables. The effect of tree size on survival varied from strongly positive for small trees (1â20 cm dbh) and medium trees (20â40 cm dbh), to slightly negative for large trees (>40 cm dbh). Among the biotic factors, we found strong evidence for negative density and frequency dependence in this temperate forest, as indicated by negative effects of both total basal area of neighbors and the frequency of conspecific neighbors. Among the abiotic factors tested, soil nutrients tended to be more important in affecting tree survival than topographic variables. Abiotic factors generally influenced survival for species with relatively high abundance, for individuals in smaller size classes and for shade-tolerant species. Our study demonstrates that the relative importance of variables driving patterns of tree survival differs greatly among size classes, species guilds and abundance classes in temperate forest, which can further understanding of forest dynamics and offer important insights into forest management
Turgor loss point predicts survival responses to experimental and natural drought in tropical tree seedlings
Identifying key traits that can serve as proxies for species drought resistance is crucial for predicting and mitigating the effects of climate change in diverse plant communities. Turgor loss point (Ïtlp) is a recently emerged trait that has been linked to species distributions across gradients of water availability. However, a direct relationship between Ïtlp and species ability to survive drought has yet to be established for woody species. Using a manipulative field experiment to quantify species drought resistance (i.e., their survival response to drought), combined with measurements of Ïtlp for 16 tree species, we show a negative relationship between Ïtlp and seedling drought resistance. Using long-term forest plot data, we also show that Ïtlp predicts seedling survival responses to a severe El Niño-related drought, although additional factors are clearly also important. Our study demonstrates that species with lower Ïtlp exhibit higher survival under both experimental and natural drought. These results provide a missing cornerstone in the assessment of the traits underlying drought resistance in woody species and strengthen Ïtlp as a proxy for evaluating which species will lose or win under projections of exacerbating drought regimes.National Science Foundation DEB-1464866, DEB-1623775, DEB-184540
Environment and Past Land Use Together Predict Functional Diversity in a Temperate Forest
Environment and human land use both shape forest composition. Abiotic conditions sift tree species from a regional pool via functional traits that influence speciesâ suitability to the local environment. In addition, human land use can modify species distributions and change functional diversity of forests. However, it is unclear how environment and land use simultaneously shape functional diversity of tree communities. Land-use legacies are especially prominent in temperate forest landscapes that have been extensively modified by humans in the last few centuries. Across a 900-ha temperate deciduous forest in the northeastern United States, comprising a mosaic of different-aged stands due to past human land use, we used four key functional traitsâmaximum height, rooting depth, wood density, and seed massâto examine how multiple environmental and land-use variables influenced species distributions and functional diversity. We sampled ~40,000 trees \u3e8 cm DBH within 485 plots totaling 137 ha. Species within plots were more functionally similar than expected by chance when we estimated functional diversity using all traits together (multi-trait), and to a lesser degree, with each trait separately. Multi-trait functional diversity was most strongly correlated with distance from the perennial stream, elevation, slope, and forest age. Environmental and land-use predictors varied in their correlation with functional diversities of the four individual traits. Landscape-wide change in abundances of individual species also correlated with both environment and land-use variables, but magnitudes of traitâenvironment interactions were generally stronger than trait interactions with land use. These findings can be applied for restoration and assisted regeneration of human-modified temperate forests by using traits to predict which tree species would establish well in relation to land-use history, topography, and soil conditions
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